Graphite fibers are of increasing interest for the construction of structural composites because of their very high strength and high stiffness to weight rations. Performance characteristics of composites depend upon the properties of the materials comprising the composite and the process by which they are combined. Full utilization of the properties of these graphite composites has not been attained because of the weakness of the interphase bonding between the fiber and the matrix. This is due in part to the type of resin used, but also to the wetting of the graphite fiber by the resin.
Generally, graphite fiber or cloth is saturated with the appropriate resin by a dip coating process. Both thermoset and thermoplastic resins have been used to prepare graphite composites. Graphite fibers have also been coated electrophoretically in non-aqueous processes to improve the wetting and impregnation of the graphite by the resin (see U.S. patent application Ser. No. 717,046, filed Mar. 28, 1985, and now U.S. Pat. No. 4,664,768. Attempts to electrophoretically coat graphite fibers from aqueous media have not been very successful because very little resin (only about 1 to 2%) is electrodeposited, and the aqueous medium is deleterious to the fiber.